Studies On Optimal Design Of APF Location And Parameters Of Output Filter

As the development of the modern grid,the equipment performance of the power transmission and distribution,the unreasonable allocation of electrical equipment,equipment interaction as well as a variety of increased non-linear load,widely used power semiconductor converter equipment and other causes make the harmonic pollution more serious.Active Power Filter(APF)is a new kind of power electronic device used to dynamically suppress harmonic and compensate reactive power.It can not only control the harmonic,but also can compensate the reactive power.Now,the studies which focus on the installation of the APF are relatively small,and are concentrated on the installation of one busbar in the system when show the effectiveness of harmonic suppression.The filter parameters are also mainly selected by experience,which will consume a lot of testing times to get more reasonable parameter values in the existing design methods.At the same time,active power filter using pulse width modulation technology will produce high-frequency switching harmonic current into the power grid,which must be eliminated using the output filter.Considering the excellent filter performance of the LCL filter in the power network,it is applied to the APF.The mathematical model of the LCL output filter in the APF is established based on this model.At the same time,the research on the output filter is often focused on the influence of the filter parameters while affect the output performance.Even if there is a small amount of literature to study its loss,it is only considered that the damping loss is the least on the basis of the basic filtering requirements.In view of these problems,the emphases of this paper are as the following:In this paper,the APF is mainly focused on the filter principle,compensation characteristics and control methods,and then APF is designed according to the corresponding filtering principle and control strategy.The validity of the designed APF is verified in the simulation system with nonlinear load.At the same time,the following applies to the case where it is specifically applied to the real power system.The better filtering effect can be obtained when the minimal harmonic current is injected,that is,the proper installation position can obtain better harmonic control effect.Therefore,finding the best installation location of APF is the key factor to obtain the optimal filtering effect.According to the calculation of the transition matrix of the bus,a large number of harmonic sources are used in the distribution network,whose frequency response characteristics of each bus are analyzed.Then the alternative busbar bank can be set up.According to the requirements of harmonics of each busbar and of the least APF,a multi-objective function model of global optimization is proposed.Finally,the optimal results can determine the optimal location and number of the installed,both to meet the filtering requirements.Unreasonable parameters will not only affect the filter performance but also reduce the efficiency of the filter system,so the practical application of the APF must be studied on the filter parameters,harmonic content,resonant frequency and damping loss.The best output efficiency also high efficiency will be gotten,that has the smallest damping loss.Considering the filter performance and APF compensation performance of LCL output filter,the optimal model of LCL filter is established,and the genetic algorithm is used to optimize the LCL filter on the basis of above research.The optimized output filter not only filters the switching harmonics effectively,but also enhances the APF compensation capability.Finally,the simulating model is built by Simulink,and the validity and superiority of the proposed method can be obtained by the comparison with the methods proposed by the relevant excellent papers.